Process for manufacturing steel from chromiferous pig-iron.



UNITED STATES PATENT OFFICE.

FRANK D, GARNEY, OF E'IEELTON, PENNSYLVANIA, ASSIGNOR TO THE PENNSYLVANIA STEEL COMPANY, OF STEELTON, PENNSYLVANIA, CORPORATION OF PENN SYLVANIAv PROCESS FOR MANUFACTURING STEEL FROM GHROMIFEROUS PIG-IRON.

Patented Oct. 27, 1908.

Application filed August 28, 1907. Serial No. 390,476.

To all whom it may concern: 7

Be it known that I, FRANK I). CARNEY, a citizen of the United States, residing at Steelton, county of Dauphin and'State of Pennsylvania, have invented a new and useful Process for Manufacturing'Steel from Chromiferous Pig-Iron, of which the following is a s ecification.

have discovered, after many experiments, that pig iron rich in chromium, produced from chromiferous ores, as a starting metal, when treated in a pneumatic converter at a comparatively low temperature, that is a tem erature" that does not reach a point at which it will reduce the products of the oxidation of the chromium and cause metallic chromium to reenter the metal, can successfully be converted into useful steel.

In carrying out my process having produced from chromiferous ores in the blast furnace, ig iron referably with a low content of s' icon, I c arge the same in a melted state into a Bessemer or other pneumatic converter. a

The pig iron with which I have had experience in carrying out my process varies in its composition, and contains as elements of interest to state, of chromium from 2% to 40%; of silicon from 0.50% to 2.00%; of manganese 0.50% to 0.80%; of phosphorus 0.15%; and of total carbon in the neighborhood of 4.50%.

The oxidation of the silicon developsheat, as is well known, early in the blow, and I have foundthat the oxidation of the chromium, likewise-develops much heat, being about one-half that 'develo ed by the oxidation of silicon, such. heat eing developed at about the same time as that from the ox'idation of the silicon, and I rely upon such heat so developed as an important part of the heat necessary to maintain theproper fluidity of the, metal.

The blowing operation should be carefully conducted, the temperature being, so controlled as not to accelerate rapidly. The temperature shouldbe maintained compara tive y low during the blow, that is, so thatas far as practicable it will not reach a oint at which the'products of oxidation of t e chromium will be reduced and metalllc chromium be causedto renterthe metal. Thls I do in the earlier part of the blow, by preferably prior to charging the melted chromiferous iron into the converter (although this may be done after the commencement of the blow) putting in the converter cold steel scrap or pig 1ron determined by weight in proportion to the chromium and silicon content of the chromiferous pig iron, so that some of the excess of heat that results from the oxidation by these elements oxidized in the earlier part of the blow, may be absorbed by the meltin of such cold metal; and during the blow' addfurther cold metal or admlt watery vapor or steam into the blast, or use any other cooling methods to maintain such comparatively low temperatureduring the blow, which terminates when the usual elimination of the carbon has been effected.

The result of the maintenance of a proper low tem erature, will be the retention, in the slag of t e products of the oxidation of the chromium.

As one way of indicating the proper temperature to be maintained, I would say that the temperature should be kept as low as possible throughout the blow, without in curring risk of skulling the teeming ladle or closing the nozzle thereof, as teeming is usually practiced in Bessemer plants.

Analysis of the metal at the end of the blow will show that the greater part of the chromium has been eliminated, and for;

some purposes this metal preferably after bein separated from the slag, may be finishe I by the addition of the usual recarburiz ing a ents for the roduction, of commercial steel avinga small content of chromium.

In carrying out my process I may use a neumatic converter with the usual acid. nin or a neurnatie converter with .the usuaIbasic lining (employing with the lat ter loose basic' material such as. lime), with similar results so far as the substantial elimination of' the chromium is concerned.

It may be desirable in some cases,.where,

as anexample, chromiferous pig iron, 'such as that wit which I have had experience before mentioned, contains 0.15 per cent. of phosphorus, and silicon-preferably below 1.25 per cent, to use a pneumatic converter with a basic lining, whereby fifty-five to seventy-five per cent. of-- such phosphorus;

can be eliminated without the usual after blow of the ordinary basic Bessemer procelements requisite to lined converter,

. either cold or in a molten state.

ess, the heat from the oxidation of the chromium enabling this to be done.

In carrying out my process in such a con verter a large proportion of the chromium is from the slag may be sub]ected to re-carburi-- zation and teemed for further manipulation. I prefer, however, to use a pneumatic acidf when the chromiferous pig iron, such as that with which I have had ex-' perience before mentioned, contains about 0.50 per cent. and upwards of silicon, on ac-' count of the cost per heat blown being less than when usin a basic lined pneumatic converter, and t eheat conditions being under better control.

For many purposes it is desirable or necessary to further treat the metal which has been subjected to my process in either kind of pneumatic converter, for the elimination of phosphorus and any small per centa e of chromium. This, if the metal has een treated in an acid lined pneumatic converter,

is done by transferring the blown metal .into a basic lined open hearth furnace into which I have charged a com aratively small quantity of usual basic s ag forming-material that is heated up prior to charging the said metal. I also charge into said furnace a comparatively small quantity ofpig iron ThlS serves to furnish the carbon and other oxidizable produce the customary boil. The process then roceeds for the elimination of the hosp orus and any small per centage of c omium uickly, the time being from about one to t ree hours, depending upon the size of the furnace. The slags formed in this process give no trouble whatever.

If the product is desired for a steel containing over 0.30% carbon and upward,'for rails, springs and the like, I preferably add at the end of the basic open hearth treatment a quantity of molten pi iron, free from chromium and having a low content of phosphorus, preferably not exceeding 0.15% with or without other recarburizing agents containing man anese. If the product is to be a low car on steel containing below 0.30% carbon, I do not add pig iron as above mentioned, but finish the metal with recarburizing agents after the metal has been tapped into the ladle.

-If the metal has been treated in a pneumatic converter-with a basic lining, it can be further treated for the elimination of any of chromium remainin therein by transferring it into acid line open hearth furnace, and then'subjectin it to the same process as that just ;descri ed .with reference to its. treatment m a basic ature.

Y eight time in open-hearth furnace matic aci lined open hearth furnace, with the exception1 that no basic slag forming material is use As a specific example, the following are the results obtained w th 24,000 lbs. of chromiferous pig iron charged in a molten state into an acid Bessemer converter. This metal contained silicon 1.44%; chromium 3.41%; phos horus0.10% andcarbon4.50%. The scrap a ded in the converter to reduce the temperature was 5,000 lbs. and the heat was blown twenty-two minutes, using steam in blast 15 minutes to keepdown the temper- The result was-metal containing 0.36% chromium,0.04% silicon,'0.09 1 phosphorus and 0.03% carbon. The Bessemer slag analyzed38.97% FeO; 28.48% sio,; 31.11%Cr,O and4.0 8% MnO. 25,000lbs. of

the blown Bessemer metal just mentioned 8.5 hearth furnace contaimng 2,000 lbs. of cold was transferred to an eighteen ton basic openchromiferous pig iron, 600 lbs. lime, 250 lbs. mill scale and 200 lbs. fluor-spar. Seventyminutes after the blown Bessemer metal was charged, 4,500 lbs. of molten hematite iron was added for recarburizing and six minutes later the heat was tapped into a ladle containing 350 lbs. ferro-manganese and 100 lbs. ferro-silicon. The: total was one hour and twenty-four minutes. the, finished metal was 31,900 lbs. T e finished metal analyzed-carbon 0.516, chromium 0.24, manganese 0.92; phosphorus 0.024; silicon 0.05 sulfur 0.07.

I claim as my'invention, and desire Letters Patent, viz:

1. The rocess iron ina pneumatic converter, and mamof manufacturing steel. which consists in blowing chromiferous pig The wei ht of taining a comparatively low temperature during the progress of, the tially as described.

2. The process of manufacturing steel which consistsin blowing chromiferous pig iron having a low content of silicon in a pneublow, substans matic converter, and maintaining a compara-' low temperature during the progress tively of th blow substantially as described.

3. he rocess of manufacturing steel which consists in blowing iron in a pneumatic acid converter, an maintaining a comparatively low temperature during the progress of .the blow substantially as described. a

4. The rocess of manufacturing steel which consists in blowing'chromiferouspig 11011 havin a low content of silicon in a-pneucomparatively low temperature during the pro ess. of the blow, substantially as de scri 5. The process of manufacturing steel which consists chromiferous pi converter, and maintaining a.

in blowing chromiferous pig 'iron in a pneumatic converte r, and malndescribed.

.taining a comparatively low temperature which consists in blowing a chromi'ferous pig iron in a pneumatic converter, at a com 'aratively lowtemperature, obtained large y by melting of scrap charged in the converter be-- fore beginning the blow, for absorbing excess of heat derived from oxidation of chromium vand silicon, substantially as described.

- 7. The process of making steel which comprlses blowing chromiferous pig iron in a pneumatic converter maintaining a comparatively low temperature during the progress of the blow, separating metal and slag and charging such blown metal into an open hearth furnace with sufficient pig iron to produce the boil and then adding pig iron free from chromium, substantially as described.

8. The process of making steel which comprises blowing chromiferous pig iron in an acid neumatic converter separating metal and s ag and charging such blown metal into anopen hearth furnace with sufficient melted pig iron to produce the boil and then adding pig iron free from chromium, substantially as 9: The process of making steel which comprises blowing chromiferous pig iron in a pneumatic converter, separating metal and slag and charging such blown metal into an open hearth furnace with sufficient pig iron to (produce the boil and then adding an iron ltion of high carbon low phosphorus pig iron free from chromium, substantially as described.

10. The process of making steel which comprises blowing chromiferous pig iron in a pneumatic converter, se arating-,metal and slag and charging such blbwn metal containing less than .60% of chromium into an open hearth furnace with suflicient pig iron to produce the boil and then adding pi iron'free from chromium, substantially as described.

11. The process of making steel which pneumatic converter, se arating metal and slag and charging such b own metal containing less than .60% of chromium into a basic open hearth furnace with sufficient melted pig iron to produce the boil to thereby heat up the bath and remove a small per centage of chromium and the phosphorus, and then adding an iron addition of high carbon low phosphorus pig iron free from chromium, substantially as described.

12. The process of making steel .which owing chromiferou's pig iron in a comprises b comprises blowing chromiferous pig iron in a pneumatic converter, separating metal and slag. and charging such blown metal containing less; than 50% of chromium into a basic open h earth furnace with sufficient cold slag and charging such metal into an open hearth furnace with sufficient chromiferous pig metal to produce a boil and adding heat to the bath by the oxidation of the chromium in the pig metal, substantially as described.

'14. The rocess of making steel which comprises b owing chromiferous pig metal in a pneumatic converter, separating metal and slag and charging such metal into an openhearth furnace with suflicient chromiferous pig metal to produce a boil and adding heat to the bath by the oxidation of'the chromi- 11111 in the pig metal, then partly recarbonizing'by the addition of the usual high'carbon low phos horus pigmetal free from chromium and nishing the steel, substantially as described.' f 15. The rocess of making steel which lbwing chromiferou's pig metal in a pneumatic converter separating metal and slag and charging such metal 1nto an open hearth furnace with sufficient chromiferous pig metal to produce a boil and adding heat tothe bath by the oxidation of the chromlum in the ig metal and finishing'the metal, substantia ly as described.

, 16. The )rocess of making steel, which comprises bl pneumatic converter, mamtalnmg a com paratively low temperature durmg the; progress of the blow, separating metal and slag, and charging such b own metal into an opens hearth furnace with sufficient pig iron to produce the boil, substantially as described.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

FRANK n OARNEY.

Witnesses M. B. PHILIPP, GEo. W. PAR'soNs.

owing chromiferous pig iron in a 

